When->buildContainer() throws because the cache directory cannot be created, we still try to write the deprecations logs inside the cache directory. In this case, the final exception isWarning: file_put_contents(/app/var/cache/dev/App_KernelDevDebugContainerDeprecations.log): failed to open stream: No such file or directory instead ofUnable to create the "cache" directory (/app/var/cache/dev)..

Alternative:

try {// ...}catch (\RuntimeException$e)}finally {if (isset($e)) {throw$e;    }// ...}